The traditional fluorescent troffer lighting fixture has through the years become a standard means for lighting interior spaces. The efficiency of fluorescent tube lighting over incandescent bulbs has been well established in the industry for decades. With the introduction of Light Emitting Diodes (LEDs), and especially high intensity LEDs, the next plateau of efficiency and convenience is presently being achieved. The power savings of LED lighting over fluorescent is well known, as are the cost benefits of a longer lasting and more reliable light source in comparison to fluorescent light, and the added benefits of a more environmentally friendly light source given the harmful levels of mercury inherent in fluorescent tubes.
It is obvious that LED light sources will eventually replace fluorescent tubes for most interior lighting, and as the fluorescent troffer is one of the most common light fixtures employing the use of linear fluorescent tubes, it is clear that the use of the existing fixture will be an efficient and cost effective structure to accommodate the new light source.
The problem that faces most replacement schemes is the characteristic differences between the fluorescent tube light source and the LED light source. Fluorescent lighting works on the principle of excitation of a gas into a plasma state wherein the entire volume of gas contained within the tube is luminous. This effect results in a widely distributed light or glow that is characterized as soft due to the wide distribution of omni-directional radiant light. An LED produces light in an almost microscopic area and the light issues forth in a radiant pattern, giving the effect that each LED in an LED array looks like a brilliant point of light. This manner of illumination is often characterized as hard or stark. The array of high contrast light produces distinctive shadows in a pattern inverse from the array of lights which are referred to as faceted shadows. The differentiating natures of the two light sources can be easily demonstrated by observing the contrast of light visible on the diffuser of a troffer fixture and in the characteristics of their shadows. The diffuser of the troffer using fluorescent tubes would have a brighter glow along the length proximate to the tube, and produce highly dispersed, or soft shadowing, light while the diffuser of the troffer employing LEDs would have a series of bright circles of high contrast, proximate to the placement of the LEDs, and produce a pattern of faceted shadows which have been characterized as distracting for people working under them.
Therefore what is needed is an LED light source replacement for the standard fluorescent troffer fixture that retains not only the energy efficiency and the decreased environmental impact but also produces a lighting effect more in line with the fluorescent having a lower contrast at the point of the diffuser and eliminating the harsh faceting that is produced by the LED's inherent light characteristics.